PROJECT SUMMARY Breast cancer is the most common cancer in women younger than 50 years, accounting for up to 25% of new breast cancer cases. Improved survival after a breast cancer diagnosis has focused attention on the critical need to address the impact of the disease and its treatments on long-term outcomes in younger women. This has become an increasingly important cancer control priority, including federal legislation focusing on the unique needs of women <45 years old. Studies have consistently shown that younger women have greater psychological and physical morbidity after breast cancer than older women and age-matched women with no cancer history, including elevated levels of depression and other behavioral symptoms (i.e., fatigue, sleep disturbance, vasomotor symptoms) that cause significant impairment in quality of life. Increased behavioral symptoms have been documented up to 10 years after diagnosis in this population, suggesting that effects may not remediate without intervention. Younger breast cancer survivors are at risk for adverse long-term effects, making them a particularly vulnerable population, for whom only a few specific interventions have been tested. A major barrier to adoption of many behavioral interventions is the lack of a translational research implementation strategy, and thus these interventions fail to become a standard of care that is clinically provided and reimbursed. To meet this challenge, we will conduct a phase III, three-group, randomized clinical trial at three geographically separated NCI-designated comprehensive cancer centers, randomly assigning 360 younger post-treatment breast cancer survivors, to one of two promising interventions (survivorship education or mindful awareness practices), comparing each to a usual care/waitlist control group. We hypothesize that both of the intervention programs will be effective in reducing behavioral symptoms (depression - primary outcome; fatigue, sleep disturbance, vasomotor symptoms-secondary outcomes) over a 6 month post- intervention period, in comparison to the usual care/waitlist control group. Additionally, we will examine the efficacy of the interventions relative to the control group on circulating and genomic markers of inflammation, hypothesizing that the mindfulness intervention will significantly reduce markers of inflammation. Finally, we will explore potential moderators of intervention efficacy in the intervention groups.